1. Field cf the Invention
This invention relates to a process for producing .omega.-hydroxy fatty acids. .omega.-Hydroxy fatty acids are useful as a raw material for synthesis of medicaments and perfumes and further are widely used as a raw material for synthesis of various polymers.
2. Related Art Statement
As a process for producing .omega.-hydroxy fatty acids, there have hitherto been proposed a process for ring-opening .omega.-hydroxyalkyl-.gamma.-butylolactone or .omega.-acyloxyalkyl-.gamma.-butylolactone (Japanese Patent Application Publication No. 61-3776), a process of converting 13-oxabicyclo [10,4,0]-hexadecene [1(12)] into a lactone and then ring-opening the lactone (Japanese Patent Application Publication No. 61-21474), and the like.
However, these processes consist of complicated and multi-stage production steps, so that the yield of the final product is low. Further, expensive raw materials are used, so that the production cost is unfavorably increased.
Moreover, there has been known a process of subjecting an ester compound or a carboxylic acid compound to a catalytic hydrogenating reduction [A. Guyer et al., Helvetica Chimica Acta, vol. 38, pp976.about.982(1955)]. However, it is not reported that a compound having an ester group and a carboxyl group in the same molecule is treated by the same manner as mentioned above to selectively reduce only the ester group. In this connection, the inventors have proposed a process in which an inexpensive dicarboxylic acid is used as a raw material and diesterified, half-hydrolyzed into a monoester and then subjected to a hydrogenating reduction in the presence of a copper-chromium oxide catalyst to form .omega.-hydroxy fatty acid (EP-A-0 262 948).